Projection optical units are known from DE 10 2012 202 675 A1, DE 10 2009 011 328 A1, U.S. Pat. No. 8,027,022 B2 and U.S. Pat. No. 6,577,443 B2. An illumination optical unit for a projection exposure apparatus is known from DE 10 2009 045 096 A1.